do you know of any books with bisexual guys where they actually say they are bi?

Yep! Whatever. by SJ Goslee and Been Here All Along by Sandy Hall have main characters who do, and All the Feels by Danika Stone and History is All You Left Me by Adam Silvera have love interests who do. (Also worth mentioning that Seven Ways We Lie by Riley Redgate has a main character who openly IDs as pansexual.)